Nitrate removal from drinking water using the ion exchange process was evaluated for a 1 mgd plant at McFarland, California. The plant supplied most of the community's water needs during 1985 and 1986. This document is the second of a two-volume report and focuses on operation and maintenance (O&M) costs and plant performance from December 1, 1984 to January 1, 1987. Volume 1 focused on plant design and the first six months of automatic operation. Actual O&M cost for the plant based on design capacity of 1 mgd was 8.5 cents per 1000 gallons. Low O&M costs are attributed to a drop in nitrate and sulfate concentrations in the source water, partial regeneration, automatic operation, and telecomputer communications for the plant. Capital cost for the nitrate removal plant was 9.9 cents per 1000 gallons when amortized over 20 years at 8% interest. Total plant cost for capital and O&M was 18.4 cents per 1000 gallons based on design capacity of 1 mgd.